Furnaces, heaters and boilers can be found in many industries such as oil refineries, petrochemical, chemical, nuclear and geothermal.
Furnaces, heaters and boilers are being used for supply of energy. Although their design may vary according to requirements of throughput, thermal conditions, fuel, building materials etc., in most cases there are some common features:
There exist a burning of a fuel with air in a combustion chamber; the air is usually supplied by a blower and the fuel enters the burning chamber through a burner. In some cases a number of burners are arranged in a structure. There exist burners mounted from different directions: from top, bottom or of the sides of the combustion chamber.
The energy of the combustion is being transferred to a fluid which flows inside enclosed tubes that are installed in the radiant section, (sometimes called “firebox”). There exist various designs of radiant sections where which tubes may be installed in many ways: vertically, horizontally, along the walls, in the middle of the firebox, and etc. After being heated, the fluid typically flows in a form of gas to a process unit which can be heat exchanger, distillation, separation or reaction where the thermal energy of the fluid can be used for distillation, separation or transferred in order to accomplish desired purpose which can be heating another process fluid, supply of energy to a reaction mixture in a chemical facility etc. In some cases, the use of a heating fluid is intended to avoid vigorous heating generated by the heat of combustion which might result in a poor control of the heat transferring process. In boilers the heated fluid is water and the product is high pressurized steam. The combustion gases (flue gases), either to be emitted or pass first through a heat recovery system, (sometimes called “convection section” or “economizer”). There are some designs where in the convection section are installed finned tubes or studded tubes to facilitate more efficient transfer of heat from the flue gases to the fluid.
Over the time, both in the radiant and in the convection sections, fuel sediments or other materials such as dust or mud that are sucked by the negative pressure that is created by the stack, are accumulated on the outside walls of the process tubes. This causes reduction in the efficiency of the heat transfer and increase in fuel consumptions and air pollution. It can also lead to problems of throughput and of process control as well as equipment damage. Scale which has high acidic or high basic pH can cause intensive corrosion of the process tube walls, which shorten the tubes work life.
Existing methods for cleaning furnaces, heaters and boilers include: sandblasting, high pressure water blasting, dry ice blasting, applying chemical agents and using steel brushes or sand paper. The present methods require inter alia a shutting down of equipment, production breaks and use of scaffolds. Those non-productive activities are leading to substantial loss of time, costs, safety hazards and disturbance in production plans.
There is a long time need to overcome the above mentioned disadvantages and negative impacts of the existing art.